1. Field of the Invention
The present invention relates to an analog electronic timepiece and a stepping motor driving method.
2. Description of Related Art
There has been an analog electronic timepiece wherein a plurality of hands are driven with a plurality of stepping motors (also called stepping motors) heretofore. In such an analog electronic timepiece, the control of fast-forwarding the hands is performed by driving the stepping motors at a high speed, in the case where the content of the information indicated by the hands is changed by changing a function, the case where the hands are returned to reference positions or are forwarded to predetermined time positions, or the like.
The fastest drive speed of each of the stepping motors for driving the hands has a limit owing to the specifications of the motor itself, the specifications of the gear train mechanism for transmitting the motion of the motor to a hand, the specifications of a drive pulse for driving the motor, and the like. Then, the maximum drive speed at which the hand can be fast-forwarded stably and efficiently is set as the fast-forward speed within the limit. In an analog electronic timepiece having a plurality of stepping motors, the fast-forward speeds set to the respective stepping motors sometimes differ from each other, one fast-forward speed being 64 pps (pulses per second: the number of drive steps for a second), and another fast-forward speed 48 pps, for example.
In conventional analog electronic timepieces, some timepieces adopted the system of performing fast-forward drives of a plurality of stepping motors in order, when fast-forwarding a plurality of systems of hands by driving the plurality of stepping motors at high speeds, as follows: the hand of a first system was first subjected to the fast-forward drive of a first stepping motor; after the completion of the fast-forward drive of the first stepping motor, the hand of a second system was subjected to the fast-forward drive of a second stepping motor; and so forth. Furthermore, some timepieces adopted the system of fast-forwarding two systems of hands together by driving a plurality of stepping motors to which the same fast-forward speed was set at the same time.
Furthermore, as a technique related to the present invention, Japanese Patent Application Laid-Open Publication No. Sho 60-162980 discloses the technique of driving two motors at the same time at a fast-forward speed which is one step lower than that at the time of fast-forwarding only the hand of one system, lest an electric power shortage should take place, when the hands of two systems are simultaneously fast-forwarded by driving the two motors.
When the hands of a plurality of systems are fast-forwarded by performing the fast-forward drives of a plurality of stepping motors, the problem exists in which the total time of the fast-forward processing becomes long, if the fast-forwarding is performed to each of the hands of systems one by one in order.
Furthermore, it can also be considered to adopt the system of fast-forwarding the hands of a plurality of systems at the same time by driving a plurality of stepping motors in parallel at the same time at different fast-forward speeds, set to the respective stepping motors, in order to shorten the time of the fast-forward processing. However, the timing control according to the fast-forward speeds becomes necessary, in order to perform the fast-forward drives of the stepping motors. Consequently, in order to drive the plurality of stepping motors at different fast-forward speeds in parallel at the same time, it becomes necessary to perform a plurality of kinds of timing control according to the different fast-forward speeds, respectively, in parallel at the same time, and the problem in which the configuration of the timing control becomes complicated is caused.